The present invention relates to a water purification plant for a swimming pool, provided with a filtering apparatus having a filtering circuit in which a filter and a pump are incorporated and via which water from the swimming pool can be circulated, and with a further circuit which is arranged parallel to at least a part of the filtering circuit and in which a UV reactor is incorporated, and with supply members for an oxidizing and disinfecting agent. The further circuit can be arranged parallel to the entire filtering circuit as well as to only a portion thereof, while the parallel circuit can further terminate in the filtering circuit itself as well as in its own connection to the swimming pool.
Such water purification plants are known. Typically, chlorine or chlorine compounds are added to the water in the swimming pool. Apart from acting as disinfectant, chlorine has an oxidizing action. It reacts both to humic acids in the make-up water, involving the formation of chlorinated organic hydrocarbons, and to organic components such as urea, creatinine and the like, introduced into the water by swimmers, involving the formation of chloramines. For that reason, apart from the amount of chlorine required for disinfecting, an additional amount of chlorine usually has to be added to compensate for the oxidizing or chlorinating action of the chlorine. In order to limit the addition of chlorine, because of the undesired formation of chlorinated organic hydrocarbons and chloramines, it has earlier been proposed to have the oxidation take place by means of ozone. Since this is a toxic gas whose remainders still have to be removed separately, the use thereof causes great problems in practice. Moreover, in that case, chlorine for disinfecting the pool water has to be added nevertheless.
Further, there is known a purification of pool water where the UV reactor is not incorporated in a separate parallel circuit, but in the filtering circuit, while, also, the organic components are oxidized by means of hydrogen peroxide, while disinfection is effected by means of the UV reactor. Although at high concentrations, hydrogen peroxide may serve as oxidizing and disinfecting agent, and a UV reactor would even be superfluous, such high concentrations in the swimming pool water are highly undesirable, in particular for swimmers. However, at low concentrations, insufficient oxidation as well as insufficient disinfection takes place. A possible solution could be provided by causing the residence time of the circulating water in a hydrogen peroxide reactor incorporated in the filtering circuit to be very long and causing the residence time in the swimming pool to be very short. However, this meets with practical drawbacks, since such hydrogen peroxide reactor would have to be particularly large, which would involve unacceptably high costs.
The use of the combination of a UV reactor and ozone as oxidant in a water purification plant as described in the preamble is also known per se. In that case, air is fed into the UV reactor, from which, under the influence of the UV radiation, ozone is obtained in situ; the ozonized air is passed through the water flowing through the UV reactor. However, the oxidizing action hereof proves to be very slight.
The object of the invention is to remove the above-mentioned drawbacks, or at least to reduce them to a considerable extent, and to provide a water purification plant wherein, in an efficient manner, both an oxidation of organic compounds introduced into the water and a sufficient disinfection of the water is obtained, while this no longer requires the addition of chlorine or other undesired substances in high concentrations, although this may in fact be desired sometimes, in particular in the case of an insufficient disinfection.
To realize this object, in a first embodiment, the water purification plant as described in the preamble is characterized in that the oxidant in the UV reactor is introduced into the water flowing through this reactor.
In a second embodiment, relating to a water purification plant for a swimming pool, provided with a filtering apparatus having a filtering circuit in which a filter and a pump are incorporated and via which water from the swimming pool can be circulated, this object is realized in that in the filtering circuit, a TV reactor is incorporated, while further, supply members for an oxidizing and disinfecting agent are present, the oxidant in the UV reactor being introduced into the water flowing through said reactor, and supply members for an additional disinfectant, such as chlorine, all types of chlorine compounds and silver salts, etc.
The oxidant is introduced into the UV reactor into the water flowing through this reactor. This can take place in the UV reactor itself, but also in the further circuit therefor, i.e. after the division in the filtering circuit. This may involve the addition of an excess of oxidant to the water; indeed, because the water, after having passed through the further conduit, is mixed with the water from the filtering circuit, while the oxidant concentration can be substantially reduced by dilution, swimmers will yet not be troubled by the added oxidant. Preferably, an oxidant is used whose oxidizing action is promoted under the influence of UV radiation.
Further advantages of the water purification plant according to the invention reside in the fact that the discharged water contains fewer chlorinated compounds, which renders the various organic compounds more readily biodegradable, while, further, less make-up water needs to be added. These advantages mean a lesser burden to the environment.
Instead of passing in situ-formed ozone through the water, which yields a poor oxidation, a direct supply of an oxidant to the water is particularly favorable. In that respect, it is important that the oxidant be water-soluble, i.e. sufficiently soluble to effect an efficient oxidation.
In particular, on the outlet side of the filter, a distribution element is present, via which a fraction (1xe2x88x92xcex1) of the pool water, wherein xcex1 lies approximately in the interval of from 0.03 to 0.5, more in particular from 0.05 to 0.2, and is preferably about 0.1, is directly returned over the filter conduit to the swimming pool and the rest of the pool water is returned to the swimming pool over the further circuit with the UV reactor. By subjecting, for instance, only 0.1 of the amount of circulated water to a direct oxidation, a very high concentration of oxidant can be introduced into the further circuit. After that, a dilution with 0.9 part of the circulated water takes place.
Further, it is particularly favorable when in the further circuit, on the inlet side of the UV reactor, make-up water is introduced. Indeed, when makeup water has to be added, as is necessary in practice, this will preferably take place where the high concentration of oxidant is added, because of the humic acids present in the make-up water.
As stated, through the features according to the invention, high concentrations of oxidant can be used without swimmers in the pool being troubled thereby. The concentration of active oxygen equivalents of the added oxidant will then be higher than the concentration of active oxygen equivalents of oxidizable organic compounds which is averagely introduced into the pool water by make-up water and by swimmers. In this respect, it is favorable when the concentration of active oxygen equivalents of the added oxidant (which can, for instance, be determined by means of potassium permanganate) is higher by a factor 2 to 100 and in particular 2 to 20, than the concentration of active oxygen equivalents of oxidizable organic compounds which is averagely introduced into the pool water by make-up water and by swimmers. In this manner, due to the high concentration of the oxidant in the second filtering circuit, an optimal oxidation of the oxidizable organic compounds introduced into the pool water is obtained, while this process proceeds considerably faster than in the case where the UV reactor were included in the first filtering circuit and the oxidant were injected therein. Further, in connection with the set UV radiation intensity, a disinfection (bacteriological equilibrium situation) can be realized.
Preferably, the oxidizing and disinfecting agent is formed by a peroxide compound, in particular hydrogen peroxide. Moreover, additionally, to meet any legal requirements concerning a prescribed degree of disinfection, a disinfectant, such as chlorine, all types of chlorine compounds and silver salts, etc., can further be added via means present for that purpose.